Disclaimer

I will use the color coding scheme which has become common among Pathfinder build handbooks. Also note that many colored items are also links to the Paizo SRD.

Red: Bad, useless options, or options which are extremely situational.

Orange: OK options, or useful options that only apply in rare circumstances

Green: Good options.

Blue: Fantastic options, often essential to the function of your character.

Temporary Note: Paizo has recently discontinued support of their official SRD. From this point forward SRD links on RPGBOT.net will instead link to d20PFSRD.com. While Archive of Nethys is now Paizo's officially licensed partner for the purposes of serving the Pathfinder SRD, Archive of Nethys is a horribly designed website and it simply doesn't match d20PFSRD's ability to keep pace with published content and d20PFSRD's search functionality.

If you encounter any links which still point to the old SRD, please email me so that I can correct them. I also recently added a page explaining my supported content which you may find helpful. --September 15, 2018

Archetypes

Spiritualist archetypes make a few significant tweaks to the class. Personally I think Fractured Mind and Haunted should be combined and considered the baseline of effectiveness for Spiritualists.

The ectoplasmatist trades the Spiritualist's defining feature (Phantom) for the ability to conjure up magic weapons. While the weapons themselves are great, nothing else about the class or the archetype meaningfully supports the Spiritualist as a martial character. You'll spend all of your feats trying to keep up with even the simplest builds of functionally similar characters like Magi.

Ectoplasmic Lash (Su): The ectoplasmist's signature feature is their ability to conjure ectoplasmic weapons. These lashes get a free enhancement bonus progression and some magic weapon properties as you gain levels, and they make decent weapons comparable to short swords, longswords, and greatswords. Keep in mind that you can't use Spiritual Combat with the two-handed option, and with only 2/3 BAB and no on-hit damage boosts like Sneak Attack the short sword-equivalents aren't useful. Generally you'll want to stick to the longsword-equivalent.

Spiritual Combat (Su): This is functionally similar to the Magus's Spell Combat ability. Unfortunately, Spiritualists lack the useful offensive options which the Magus gets, so you have very few spells which work well with this ability.

Ectoplasmic Armor (Su): Too little, too late. By this level you should be wearing at least +1 Chain Shirt.

The Spiritualist is in dire need of a clear role within a party. Fractured Mind makes the Spiritualist a viable face, but also replaces the Spiritualists spell-like abilities (all of which were spells Spiritualists could already cast) with a new list of spell-like abilities.

Emotional Spellcasting: Switching the Spiritualist from a Wisdom-based spellcaster to a Charisma-based spellcaster suddenly makes them a decent Face. Spiritualists already have most of the Face skills, but typically dump Charisma because it does nothing useful for them except skills. Pick up Diplomacy with a trait and you're good to go.

Emotional Power (Sp): All of the spell-like abilities which this replaces are spells that are already on the Spiritualist spell list, which made the abilities totally pointless. Literally any one of these options is better than the vanilla Spiritualist.

Anger (Su): Fine spells, but none of them help you and most of them can't target your Phantom.

Dedication (Su): Excluding command, every spell is an option which will be useful at any level.

Despair (Su): With the exception of Stricken Heart, all of these spells allow saving throws. You are not a supremacy caster.

Fear (Su): All of these spells allow saving throws. You are not a supremacy caster.

Hatred (Su): All of these spells allow saving throws. You are not a supremacy caster.

Give up the ability to manifest your Phantom in Ectoplasmic form in exchange for... well, not a lot to be honest. You could accomplish almost everything that the Geist Channeler can do by taking the Fear Emotional Focus and casting telekinesis.

Geistform Phantom (Su): Ectoplasmic is typically the more useful of the two manifestation modes, and your Phantom gives up half of its damage output.

Emotionless (Su): Emotionless works just like an Emotion Focus.

Unnerving Touch (Su): Making creatures shaken is great, but until about 5th level that's basically the only thing your Phantom can do.

I don't like Bonded Manifestation. It's a pointless ability that's only useful as a fallback when you can't manifest your Phantom. Instead, trade it in for the ability to temporarily buff your Phantom when you really need it to murder some stuff.

Usurp Manifestation (Su): Increasing your Phantom's size is a useful improvement to your Phantom's damage output, and the natural armor bonus offsets the AC it will lose from changing size. You'll be nauseated, but you weren't going to do anything useful on your turn anyway so you might as well spend your turn vomiting.

Usurp Spell: You don't want to use this too often because it eats through your spell slots twice as fast as normal, but sometimes you need to buff or heal your Phantom in a hurry.

Teleplasmic Surge: Always great at no new cost.

Ferocious Phantom: DR 10/slashing is nice because by this level a lot of enemies will have the ability to bypass your Phantom's DR 10/magic.

Access to cleric spells can make the Spiritualist a passable healer, especially since they already have access to Cure spells, but to 2/3 spellcasting means that you'll often get solutions to other problems long after your group starts needing them.

Divine Spellcasting: Switching from psychic to divine spellcasting usually won't be a problem, but it does mean that you need a hand free to perform somatic components and you need to speak aloud.

Spiritual Resistance (Su): Too situational.

Divine Teachings (Su): Access to cleric spells is great, but it's frustrating that you can only use them while your spirit is confined.